Thanks for the query.
Ingrown hairs may present with pus filled lesions
But it is unlikely to present as blisters.
There can be two possibilities of your condition.
1. contact dermatitits, as you mentioned using a new soap.
Tests are required to know the exact cause
A photograph would have helped me better.
Please meet a dermatologist
for exact diagnosis.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.